You have to watch out for all these vendors on shipping charges. Some charge lower product prices and make up profit by charging more for shipping. Others charge a higher price and reasonable shipping cost. You have to consider the cost of boxes, envelopes and shipping material into the cost of shipping - they're not free to the seller.
I have to agree that $9 for shipping an O-ring is outrageously high.
Looks like Bicycle-Engines.com is back ordered on the carburetors.